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Technical Document 1 Attached to the European XFEL Convention Executive Summary of the Technical Design Report (Part A) and Sc

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Technical Document 1 Attached to the European XFEL Convention Executive Summary of the Technical Design Report (Part A) and Sc May 30, 2007 Technical Document 1 attached to the European XFEL Convention Executive Summary of the Technical Design Report (Part A) and Scenario for the Rapid Start-up of the European XFEL Facility (Part B) Introduction The XFEL Technical Design Report (TDR), adopted by the XFEL Steering Committee in July 2006, foresees a facility comprising an accelerator complex for an electron energy of up to 20 GeV (17.5 GeV in the standard operation mode), five undulator branches with ten experimental stations, and various office, laboratory and general utility buildings distributed over three different sites. An executive summary of the TDR is given in part A of this Annex to the “Convention concerning the construction and operation of a European X-ray Free- Electron Laser Facility” (XFEL Convention). The total project cost of the XFEL Facility as set out in the Technical Design Report (TDR) and in Annex 3 to the XFEL Convention amounts to 1081.6 M€, out of which 38.8 M€ for the preparation, 986.4 M€ for construction and 56.4 M€ for commissioning (all in 2005 prices). In order to begin the construction as early as possible, the Contracting Parties agreed that the facility be realised in steps, with initial commitments covering only the costs of the first step. The construction costs for the first step were set at approximately 850 M€ (instead of 986.4 M€). In part B of this Annex the characteristics of the rapid start-up scenario of the XFEL project are briefly outlined. A reference configuration, corresponding to a construction cost of 850 M€ is described; this configuration is not unique and alternative ones, all of which have construction costs not exceeding 850 M€, are also exemplified. A timeline for the final decision on the adoption of a specific configuration is also indicated. All alternatives are upgradeable to the full facility as described in the TDR. Part A of Technical Document 1 EXECUTIVE SUMMARY of the TECHNICAL DESIGN REPORT ii Executive Summary Executive Summary 1 Basic Objectives This report contains a full technical description of the European X-ray Free-Electron Laser Facility, a new international scientific infrastructure to be built in the north west of Hamburg. The purpose of the facility is to generate extremely brilliant (peak brilliance ~ 1033 photons/s/mm2/mrad2/0.1%BW), ultra-short (~ 100 fs) pulses of spatially coherent x-rays with wavelengths down to 0.1 nm, and to exploit them for revolutionary scientific experiments in a variety of disciplines spanning physics, chemistry, materials science and biology. The design contains a baseline facility and provisions to facilitate future extensions and improvements, in preparation of further progress in the relevant technologies. The basic process adopted to generate the x-ray pulses is SASE (Self-Amplified Spontaneous Emission), whereby electron bunches are generated in a high-brightness gun, brought to high energy (up to 20 GeV) through a superconducting linear accelerator, and conveyed to long (up to ~200 m) undulators where the x-rays are generated. Five photon beamlines deliver the x-ray pulses to ten experimental stations, where state-of-the-art equipment is available for the experiments. From this new user facility, novel results of fundamental importance can be expected in materials physics, plasma physics, planet science and astrophysics, chemistry, structural biology and biochemistry, with significant possible impact on technologies such as nuclear fusion, catalysis, combustion (and their environmental aspects), as well as on biomedical and pharmaceutical technologies. Thanks to its superconducting accelerator technology, in spite of competing American and Japanese projects, the European X-ray Free-Electron Laser Facility will allow Europe to keep its leadership in basic and applied science with accelerator-based light sources, a leadership it acquired in the early 90’s with the construction and operation of the European Synchrotron Radiation Facility (ESRF) in Grenoble. 2 History of the Project The basic technology underlying the European X-ray Free-Electron Laser Facility is the superconducting linear accelerator technology, developed by an international collaboration coordinated by the DESY laboratory in Hamburg, with the initial objective to create TESLA (Tera-Electronvolt Superconducting Linear Accelerator), an electron-positron linear collider with TeV energy, for particle physics studies, hence the name TESLA technology. It was soon realized that this type of innovative linear accelerator had ideal characteristics for an x-ray free-electron laser. Proposals to build a free-electron laser, first as a side branch of the linear collider, and later as a self-standing facility were put forward by DESY to the German government. The construction of a test facility (TESLA Test Facility 1, or TTF1) was undertaken, and lasing down to ~90 nm wavelengths was successfully demonstrated in 2000. TTF2 had the more ambitious goal to push lasing to 6 nm wavelengths, with a 1 GeV linear accelerator. This should be achieved in 2007; in the meantime, acceleration of electrons up to 0.75 GeV has obtained lasing at 32 nm (Jan. 2005) and at 13 nm (April 2006), and a vigorous user program was started in August 2005 in the experiments hall downstream from the free- electron laser, forming what is now called the FLASH facility. In 2003, the German government decided to launch the proposal to constitute a European Facility for the construction and operation of an x-ray free-electron laser in Hamburg, undertaking the Executive Summary iii commitment to finance the new facility by providing up to 60% of its construction costs, and up to 40% of the operation costs. The choice of the location in Hamburg is motivated by the possibility to take advantage of the unique experience and know-how of the DESY Machine Division in the area of superconducting linacs, and of the possibility to gain first-hand experience on the operation of an FEL through the FLASH facility. 3 The Scientific Case and the X-ray FEL Interna- tional Context All natural sciences benefit from the use of photons (light waves) of different wavelengths to probe the phenomena of nature. The use of infrared, visible and near ultraviolet light has been revolutionized by the invention of gas lasers and of solid-state lasers, with their properties of high brilliance, spatial coherence and, in more recent decades, ultrashort pulses, with duration down to a few femtoseconds or less (1 femtosecond, or 1 fs, equals a billionth of a millionth of a second; light travels a distance of 0.3 μm in 1 fs). This time scale is of particular importance because atoms in molecules and solids oscillate around their equilibrium positions with typical periods of a few hundreds of fs, and in general, movements of atoms during the rearrangement of their positions in chemical reactions, or phase transformations also occur on such a time scale. In the range of the ultraviolet, soft x-ray and hard x-ray wavelengths, great progress was achieved by the exploitation of synchrotron radiation, the brilliant emission by electrons or positrons orbiting in a circular accelerator. Synchrotron radiation, however, is far less brilliant than a powerful laser, has a very limited degree of spatial coherence, and it comes typically in pulses of ~ 30 ps = 30,000 fs duration. The objective of the modern projects for the realization of x-ray free-electron lasers is the extension of the scientific and technological revolution, ushered by lasers in the visible light range, to the x-ray range, providing spatially coherent pulses of < 100 fs duration, with peak powers of many GW. As discussed in four international workshops organized between October 2005 and March 2006 in Hamburg, Paris, Copenhagen, and near Oxford, the outstanding properties of the European XFEL beams (coherence, ultra-high brilliance and time structure) and the development of appropriate detectors and instrumentation will allow completely new experiments. A few examples are listed below. Coherence can be used for holographic and lensless imaging in materials science and in biology. Spectacular possibilities open up, as detailed theoretical studies and simulations predict that, with a single very short and intense coherent x-ray pulse from the XFEL, a diffraction pattern may be recorded from a large macromolecule, a virus, or a cell, without the need for crystalline periodicity. This would eliminate a formidable bottleneck for many systems of high interest, e.g. membrane proteins, viruses and viral genomes. Measurement of the over-sampled x-ray diffraction pattern permits phase retrieval and hence structure determination. Although individual samples would eventually be destroyed by the very intense x-ray pulse, a three-dimensional data set could be assembled, when copies of a reproducible sample are exposed to the beam one by one. The high intensity can also be used to produce highly ionized states of atoms, generating in the laboratory conditions and processes occurring in interstellar gases. In conjunction with the ultra short pulse duration, it can be exploited in pump-and-probe experiments, where conventional laser pulses (pump) are used to trigger a chemical reaction or a phase transition, iv Executive Summary and the XFEL pulses (probe), each following the pump pulse with a well determined delay (from ~50 fs up to ns or even μs), provide a “movie” of the atomic displacements and rearrangement of chemical bonds. In this way, catalytic mechanisms in chemical and biochemical reactions can be elucidated, fast reactions (e.g. combustion) can be subject to detailed investigation, nucleation of ordered phases at phase transitions can be imaged, and hitherto inaccessible states of matter can be brought to experimental investigation: if the pump pulse is sufficiently powerful to produce a plasma, the x-ray pulse can still penetrate the highly ionized medium (opaque to visible light) and provide information on the propagation of the shock front, on the time evolution of temperature and pressure distributions, on the equation of state.
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